ATC

TROUBLE DIAGNOSIS


Ambient Sensor Circuit


COMPONENT DESCRIPTION

Ambient Sensor
The ambient sensor is attached on the radiator core support (driver side). It detects ambient temperature and converts it into a resistance value which is then input into the front air control.






AMBIENT TEMPERATURE INPUT PROCESS
The front air control includes a processing circuit for the ambient sensor input. However, when the temperature detected by the ambient sensor increases quickly, the processing circuit retards the front air control function. It only allows the front air control to recognize an ambient temperature increase of 0.33�C (0.6�F) per 100 seconds.
This prevents constant adjustments due to momentary conditions, such as stopping after high speed driving.
Although the actual ambient temperature has not changed, the temperature detected by the ambient sensor will increase. This is because the heat from the engine compartment can radiate to the front grille area, location of the ambient sensor.

DIAGNOSTIC PROCEDURE FOR AMBIENT SENSOR






SYMPTOM: Ambient sensor circuit is open or shorted. Using the CONSULT-III, DTC B257B or B257C is displayed. Without a CONSULT-III, code 40 or 41 is indicated on front air control as a result of conducting the front air control self-diagnosis.
1.CHECK VOLTAGE BETWEEN AMBIENT SENSOR AND GROUND





1. Disconnect ambient sensor connector.
2. Turn ignition switch ON.
3. Check voltage between ambient sensor harness connector E1 terminal 2 and ground.

Approx. 5V

OK or NG
OK - GO TO 2.
NG - GO TO 4.
2.CHECK CIRCUIT CONTINUITY BETWEEN AMBIENT SENSOR AND FRONT AIR CONTROL





1. Turn ignition switch OFF.
2. Disconnect front air control connector.
3. Check continuity between ambient sensor harness connector E1 (B) terminal 1 and front air control harness connector M49 (A) terminal 26.

Continuity should exist.

OK or NG
OK - GO TO 3.
NG - Repair harness or connector.
3.CHECK AMBIENT SENSOR
Check ambient sensor. Refer to "Ambient Sensor".
OK or NG
OK - 1. Replace front air control. Refer to Service and Repair.
2. Go to A/C System Self-Diagnosis Function and perform self-diagnosis.
NG - 1. Replace ambient sensor. Service and Repair.
2. Go to A/C System Self-Diagnosis Function and perform self-diagnosis.
4.CHECK CIRCUIT CONTINUITY BETWEEN AMBIENT SENSOR AND FRONT AIR CONTROL





1. Turn ignition switch OFF.
2. Disconnect front air control connector.
3. Check continuity between ambient sensor harness connector E1 (B) terminal 2 and front air control harness connector M49 (A) terminal 25.

Continuity should exist.

4. Check continuity between ambient sensor harness connector E1 (B) terminal 2 and ground.

Continuity should not exist.

OK or NG
OK - 1. Replace front air control. Refer to Service and Repair.
2. Go to A/C System Self-Diagnosis Function and perform self-diagnosis.
NG - Repair harness or connector.

COMPONENT INSPECTION

Ambient Sensor






After disconnecting ambient sensor connector, measure resistance between terminals 2 and 1 at sensor component side, using the table below.






If NG, replace ambient sensor. Refer to Service and Repair.